The inclusive production rate of neutral pions in the rapidity range greater than $y=8.9$ has been measured by the Large Hadron Collider forward (LHCf) experiment during LHC $\sqrt{s}=7$\,TeV proton-proton collision operation in early 2010. This paper presents the transverse momentum spectra of the neutral pions. The spectra from two independent LHCf detectors are consistent with each other and serve as a cross check of the data. The transverse momentum spectra are also compared with the predictions of several hadronic interaction models that are often used for high energy particle physics and for modeling ultra-high-energy cosmic-ray showers.
Production rate for PI0 production in the rapidity range 8.9-9.0.
Production rate for PI0 production in the rapidity range 9.0-9.2.
Production rate for PI0 production in the rapidity range 9.2-9.4.
The transverse momentum ($p_\text{T}$) distribution for inclusive neutral pions in the very forward rapidity region has been measured, with the Large Hadron Collider forward detector (LHCf), in proton--lead collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_{NN}} = 5.02$TeV at the LHC. The $p_\text{T}$ spectra obtained in the rapidity range $-11.0 < y_\text{lab} < -8.9$ and $0 < p_\text{T} < 0.6$GeV (in the detector reference frame) show a strong suppression of the production of neutral pions after taking into account ultra-peripheral collisions. This leads to a nuclear modification factor value, relative to the interpolated $p_\text{T}$ spectra in proton-proton collisions at $\sqrt{s} = 5.02$TeV, of about 0.1--0.4. This value is compared with the predictions of several hadronic interaction Monte Carlo simulations.
Production rate for PI0 production in the rapidity range -8.9 to -9.0.
Production rate for PI0 production in the rapidity range -9.0 to -9.2.
Production rate for PI0 production in the rapidity range -9.2 to -9.4.
The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC $\sqrt{s}$ = 7 TeV proton--proton collisions with the pseudo-rapidity $\eta$ ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the difference in the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However no model perfectly explains the experimental results in the whole pseudo-rapidity range. The experimental data indicate the most abundant neutron production rate relative to the photon production, which does not agree with predictions of the models.
Differential neutron production rate d$\sigma_{n}$/dE [mb/GeV] for each rapidity range.
The differential cross sections for inclusive neutral pions as a function of transverse and longitudinal momentum in the very forward rapidity region have been measured at the Large Hadron Collider (LHC) with the Large Hadron Collider forward detector (LHCf) in proton-proton collisions at $\sqrt{s}=$ 2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of $\sqrt{s_\text{NN}}=$ 5.02 TeV. Such differential cross sections in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. Comparing proton-proton with proton-lead collisions, we find a sizable suppression of the production of neutral pions in the differential cross sections after subtraction of ultra-peripheral proton-lead collisions. This suppression corresponds to the nuclear modification factor value of about 0.1-0.3. The experimental measurements presented in this paper provide a benchmark for the hadronic interaction Monte Carlo simulation codes that are used for the simulation of cosmic ray air showers.
The average $\pi^{0}$ transverse momenta for the rapidity range $8.8<y<10.6$ in $p+p$ collisions at $\sqrt{s}=2.76$ and 7 TeV and for the rapidity range $-8.8>y_\rm{lab}>-10.6$ in $p+\rm{Pb}$ collisions at $\sqrt{s_\rm{NN}}=5.02$ TeV. The rapidity values for $p+\rm{Pb}$ collisions are in the detector reference frame and must be multiplied by -1.
Production rate for the $\pi^{0}$ production in the rapidity range $8.8 < y < 9.0$ in $p+p$ collisions and in the rapidity range $-8.8 > y_\rm{lab} > -9.0$ in $p+\rm{Pb}$ collisions.
Production rate for the $\pi^{0}$ production in the rapidity range $9.0 < y < 9.2$ in $p+p$ collisions and in the rapidity range $-9.0 > y_\rm{lab} > -9.2$ in $p+\rm{Pb}$ collisions.
We have made a precise measurement of the cross section for e + e − →Z 0 →hadrons with the L3 detector at LEP, covering the s range from 88.28 to 95.04 GeV. From a fit to the Z 0 mass, total width, and the hadronic cross section to be M Z 0 =91.160 ± 0.024 (experiment) ±0.030(LEP) GeV, Γ Z 0 =2.539±0.054 GeV, and σ h ( M Z 0 )=29.5±0.7 nb. We also used the fit to the Z 0 peak cross section and the width todetermine Γ invisible =0.548±0.029 GeV, which corresponds to 3.29±0.17 species of light neutrinos. The possibility of four or more neutrino flavors is thus ruled out at the 4σ confidence level.
No description provided.
Total hadronic cross section.
We report the results of first physics runs of the L3 detector at LEP. Based on 2538 hadron events, we determined the mass m z 0 and the width Γ z 0 of the intermediate vector boson Z 0 to be m z 0 =91.132±0.057 GeV (not including the 46 MeV LEP machine energy uncertainty) and Γ z 0 =2.588±0.137 GeV. We also determined Γ invisible =0.567±0.080 GeV, corresponding to 3.42±0.48 number of neutrino flavors. We also measured the muon pair cross section and determined the branching ratio Γ μμ = Γ h =0.056±0.006. The partial width of Z 0 →e + e − is Γ ee =88±9±7 MeV.
No description provided.
We have measured both the rates and the forward-backward asymmetry of ℓ + ℓ − from Z 0 →ℓ + ℓ − (where ℓ= μ , τ ) with the L3 detector. We obtained Γ ℓℓ =88±4±3 MeV and the vector neutral current coupling constant, g v =0.00±0.07 and the axial vector neutral current coupling constant, g A =−0.515±0.015.
No description provided.
No description provided.
We have measured the properties of Z 0 → b b decays using a sample of 944 inclusive muon events, corresponding to 18 000 hadron events obtained with the L3 detector at LEP. We measured the partial decay width of the Z 0 into b b , Γ b b =353±48 MeV , and we determined the vector coupling of the Z 0 to the b quark; g rmv 2 (b)=0.095±0.047. We measured the forward-backward charge asymmetry in e + e − → b b events at √ s ≈ M v , and obtained A b b =13.3±9.9% .
BOTTOM quark charge asymmetry measurement.
We have measured the partial width and forward-backward charge asymmetry for the reaction e + e - →Z 0 →μ + μ - (γ). We obtain a partial width Γ μμ of 83.3±1.3(stat)±0.9(sys) MeV and the following values for the vector and axial vector couplings: g v =−0.062 −0.015 +0.020 and g A =−0.497 −0.005 +0.005 . From our measurement of the partial width and the mass of the Z 0 boson we determine the effective electroweak mixing angle, sin 2 θ w =0.232±0.005, and the neutral current coupling strength parameter, ϱ =0.998±0.016.
No description provided.
Forward backward charge asymmetry.
No description provided.
We have measured the cross section for e + e − →hadrons over the center of mass energy range of the Z 0 peak, from 88.22 to 95.03 GeV. We determine the Z 0 mass M z =91.164±0.013 (experiment) ±0.030 (LEP) GeV. Within the framework of the standard model we determine the invisible width, Γ invisible =0.502±0.018 GeV, and the number of light neutrino species, N ν =3.01±0.11. We exclude the existence of a supersymmetric scalar neutrino having a mass less than 31.4 GeV, at the 95% confidence level. We performed a model independent combined fit to the e + e − →hadrons and e + e − → μ + μ − data to determine total width, leptonic width and hadronic width of the Z 0 .
Cross sections from 1990 data. Additional systematic error 1.5 pct.
Cross sections from 1989 data. This data has been rescaled by 0.96 from original publication PL B237 (90) 136. Additional systematic error 2.0 pct.
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